Synergetic Effect between Limbs and Spine Dynamics in Quadruped Walking Robots

In this paper, in order to meet the requirements of stable foot support and balanced walking of quadruped hydraulic robot, a new control method is proposed. The "hard" contact between the feet of the quadruped hydraulic robot and the ground are changed into "semi flexible" contact to reduce the impact force produced by the contact and collision of the two and reduce the unbalance of the force. The designed "semi flexible" scheme was to coat the "semi flexible" modified polytetrafluoroethylene (PTFE) material on the surface of the bottom material of the robot's foot. The modification of PTFE was optimized by SRIM, and the optimization scheme was selected for experimental study to obtain the Al2O3/PTFE material for which the abrasive resistance met the requirement of robot motion. It was also used in robot force imbalance control experiment research optimization. The study clearly revealed that it can effectively reduce the power of the impact force caused by the contact and collision of the feet of the quadruped robot and the ground, reduce the swing and the unbalance of the motion force of the quadruped robot, and meet the requirements of the precise positioning and the force balance walking of the motion of quadruped hydraulic robot to a certain extent.

We have proposed the sway compensation trajectory of robot body to realize dynamically stable walking for a quadruped walking robot. This method uses the lateral motion of the robot body to keep a zero momentum point (ZMP) on a diagonal line between the support legs. However, energy consumption of the sway compensation trajectory is larger than the case without trajectory control because periodical acceleration of the body has to be generated to realize sway motion. In this paper, we propose a new sway compensation trajectory for a quadruped walking robot named 3D sway compensation trajectory. This method is the extension of conventional sway compensation trajectory toward three dimensional motion, and the position of ZMP is controlled not only by lateral body motion but also by longitudinal and vertical body motion. Next, we demonstrate that energy consumption for walking can be reduced by combining these motions through theoretical analysis and computer simulation, and an optimum 3D sway compensation trajectory that minimizes energy consumption is proposed. Optimum trajectory is applied to a quadruped walking robot and the validity of the proposed trajectory is verified using the dynamic motion simulator, ADAMS.

This paper investigates dynamic gait planning optimization and balance control of quadruped robots under external disturbance forces. First, a platform of quadruped walking robot with fourteen active degrees of freedom is designed. Then, a forward kinematic model of joints is built for quadruped robots based on Denavit-Hartenberg(D-H) method. The inverse kinematic equations are solved to result in joint values when the desired position and orientation are specified. A dynamic gait planning algorithm is proposed and tested on the quadruped robot. The planning function is established to create some point-to-point trajectories. The angle values of the joints can be calculated by using the inverse kinematics equations for every moment. Considering the external distribution a balance control approach is proposed to stabilize the robot based on the information from the attitude sensors. The walking is stabilized by a feedback control that uses a three-axis acceleration sensor. Experiments have been performed on the quadruped robot. The results showed that the proposed methods work well in dynamic gait planning and external disturbances of a quadruped bionic robot.

For an easier and natural teleoperation of the quadruped walking robots, a user interface is developed with a steering wheel and an assembly of pedals. In order to change the speed and the direction of the quadruped walking robots according to the operation of the steering wheel and the pedal, an online gait transition method is developed. Using this human-machine interface and online gait transition, the operator can control the quadruped walking robots almost in the same way as a driver drives a car. A quadruped walking robot named JROB-2 is used in the experiments. As the steering wheel is also equipped with various control buttons, it is possible to assign various single command tasks, like stand up and sit down etc., to these buttons and hence control the robot for these tasks without even touching the keyboard or mouse. The paper presents the details of this interface.

This paper proposes a quadruped walking robot that has high performance as a working machine. This robot is needed for various tasks controlled by tele-operation, especially for humanitarian mine detection and removal. Since there are numerous personnel landmines that are still in place from many wars, it is desirable to provide a safe and inexpensive tool that civilians can use to remove those mines. The authors have been working on the concept of the humanitarian demining robot systems for 4 years and have performed basic experiments with the first prototype VK-I using the modified quadruped walking robot, TITAN-VIII. After those experiments, it was possible to refine some concepts and now the new robot has a tool (end-effector) changing system on its back, so that by utilizing the legs as manipulation arms and connecting various tools to the foot, it can perform mine detection and removal tasks. Toaccomplish these tasks, we developed various end-effectors that can be attached to the working leg. In this paper we will discuss the mechanical design of the new walking robot called TITAN-IX to be applied to the new system VK-II.

A new method, inspired by the gait of horses, for regulating the ground reaction force of a quadruped walking robot, is proposed. The method uses the mechanical stiffness switch with a dual‐spring structure inspired by an equine distal forelimb. This includes the use of a low‐stiffness spring activated at the moment of touchdown and a high‐stiffness spring for the support phase. This method has been applied to Jinpoong, a hydraulic quadruped walking robot, and has contributed to the robot's stable gait on uneven terrain.

Reduction of the energy consumption is one of the most important problems to utilize quadruped walking robots for various works on rugged terrain. The authors have studied basic strategy to achieve high energy efficiency when the quadruped walking robot do the motion essentially requires positive power by the analysis of body rising motion. This paper discusses the energy efficiency of the slope walking motion by the quadruped walking robot. First, we investigate the walking posture in consideration of ideal actuator characteristics where the robot consumes few negative powers at each joint which causes the main energy loss of the walking robot. Then, we investigate optimal walking posture in consideration of DC motor characteristics by the full search of three gait parameters which define the crawl gait. Furthermore, we derive the optimal walking motion by the optimization of three gait parameters which are kept constant during one cycle gait and instantaneous parameters such as body velocity and supporting forces changed at each moment simultaneously.

Dynamic walking is often required in a quadruped robot for the purpose of quick locomotion. It is generally known that the walking pattern of animals is changed to the trot or the pace in middle speed locomotion. Trot walking was recently studied by several groups because of its stability. In the trot, diagonal legs form pairs. While one pair of legs provides support, the other pair of legs swings forward in preparation for the next step. In the trot of the quadruped robot with point-support feet, a rotation around a diagonal line formed by the supporting leg can't be controlled directly by using torques at the articular joints. In this paper, the 3D behavior in trot walking is analyzed from the viewpoint of foot force, duty factor and the roll angle of the body. The effects of the stance and the center of gravity of the body are also examined experimentally using our quadruped robot 'COLT-2.'

This paper describes a quadruped walking robot with hydraulic driving. The model of the quadruped robot is built by ADAMS and the link coordinate system of the quadruped robot's leg is established based on the D-H parameter method with kinematics equations established. A hydraulic control system model is established by the theoretical analysis of the hydraulic system, and the stable walking of quadruped robot is simulated by using the joint simulation of MATLAB and ADAMS.

In this paper, we introduce an intelligent quadruped walking robot that can perform stable walking and a couple of intelligent behaviors. The developed robot has two sets of ultrasonic sensors and six sets of infrared sensors and can perform obstacle avoidance by detecting obstacles and estimating the distances and directions of those obstacles. The robot also has a stereo camera and can paly soccer by detecting a ball and estimating the 3 dimensional coordinates of the ball. In performing those intelligent behaviors, the robot needs to have the capability of generating its walking patterns, solving the inverse kinematics problem, and interfacing several sensors in realtime. Therefore we designed a hierarchical controller that consists of a main controller and an auxiliary controller. The main controller is a 32-bit DSP that can perform fast floating-point opertaion and the auxiliary one is a 8-bit micro-controller. We showed that the developed quadruped walking robot successfully perform those intelligent behaviors through experiments.

In this paper, walking motion learning of quadrupedal walking robot is realized by the Profit Sharing that can learn deterministic policy for POMDPs environments. In this research, we used the Profit Sharing that can learn deterministic policy for POMDPs environments which can obtain the deterministic policy by using the history of observations. We carried out a series of experiments using quadrupedal walking robot, and confirmed that walking motion learning can be realized by the Profit Sharing that can learn deterministic policy for POMDPs environments.KeywordsAction SelectionObservation SequenceAverage RewardDeterministic RateWalking MotionThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

In this paper, the modelling and analysis problem of a planar quadruped walking robot with eight degrees of freedom using singular system theory is investigated. First, a brief description about singular system is given and then, the singular model of the quadruped robot is derived. Because of the complexity of the singular model of the robot, we linearized it around the contact point of the leg and the ground, and based on this model it is shown that impulses are generated in the force which exists between leg and ground in the contact points.

Quadruped walking robots need to handle high obstacles like steps that are often not kinematically reachable. We present a dynamic leap that allows a quadruped robot to put its front legs up onto a high rock or ledge, a motion we have found is critical to being able to locomote over rough terrain. The leaping motion was optimized using a simulated planar quadruped model. We present experimental results for the implementation of this optimized motion on a real quadruped robot.

This paper presents a motion planning algorithm of static walking gait for a quadruped robot. First, the kinematics and dynamics equations of quadruped are built which can be used to research legged locomotion. Based on kinematics equations, foot trajectory is proposed with some optimization methods. Then the problem of redundant freedom in the joint angle is solved through dynamic optimization. Finally, the quadruped robot walking is realized by MATLAB calculation and ADAMS simulation.

In this paper, we consider the problem of planning a feasible path for a quadruped walking robot in an environment of obstacles. In conventional path-planning problems, the main focus is merely collision avoidance with obstacles since a wheeled robot is involved. However, in the case of a legged robot, both collision avoidance and crossing over obstacles must be taken into account in the process of path planning. Furthermore, the constraints of the gait should be considered to guarantee the feasibility of a planned path. To resolve this complicated problem in a systematic way, a new concept of an artificial thermal field is proposed. Specifically, with the assumption that a robot walks with a periodic crab gait, a robot and obstacles in a three-dimensional (3D) space are projected on a 2D plane. Next, the 2D obstacles are transformed into the configuration space of a quadruped robot. A feasible path is finally sought in an artificial thermal field which is constructed numerically on the discretized configuration space. To verify the efficacy of the proposed approach, three notable simulation results are provided.